Screening of monoamine oxidase B inhibitors in Tibetan strawberry by ligand fishing based on enzyme functionalized cellulose filter paper

Tibetan strawberry (Fragaria nubicola) is a wild medicinal and edible plant in Tibet possessing various health benefits such as neuroprotection and anti-oxidation. However, there has been little study reported on its chemical constituents. To investigate the inhibitors of monoamine oxidase B (MAO-B) in Tibetan strawberry, we immobilized the enzyme onto cellulose filter paper for the first time to develop a new screening method. Two known glycosides (compounds 1 and 2) and one new iridoid glucoside (Compound 3) were fished out by this method, which was found to effectively inhibit MAO-B with IC50 values of 16.95 ± 0.93, 24.69 ± 0.20, and 46.77 ± 0.78 μM, respectively. Molecular docking and kinetic analysis were performed to reveal the inhibition mechanism of these compounds. Furthermore, compound 1 exhibited neuroprotective effects against 6-OHDA-induced injury on PC12 cells. The developed method exhibits the advantages of rapidness and effectiveness in screening of MAO-B inhibitors from complex herbal extracts.